This invention relates to a hand tool for the preparation of bores for use of blind fasteners in sheet material wherein the bore has an off-set countersunk recess.
In the preparation of sheet material or thin structural plate members for the reception of blind fasteners it has been the general practice to drill a hole completely through the plate member and thence if necessary to countersink the hole to facilitate the securing of a blind fastener thereto. The present invention is directed to a tool that is readily portable and can efficiently prepare sheet material for the reception of a uniquely constructed blind fastener. The fastener has an upper hollow head portion that tapers to a tubular body portion wherein the central axis of the tapered head is off-set from the axis of the central bore of the tubular body portion. To install such fastener it is necessary to first perform a countersinking operation and then drill the bore so that its axis is off-set from the central axis of the countersunk recess. The use of a fastener as described in such a counter-sunk bore combination is that such fastener can be installed quickly and conveniently without concern for any rotation of the fastener due to its off-set head. The present invention is directed to a hand tool for use in preparing the off-set bore with its countersunk recess or upper portion wherein the tool expedites the preparation of the fastening operation where the fastener is subjected to high torques. The tool of the instant invention provides a more accurate means for expediting the preparation of such fastening operations, and a handle connected to said pilot sleeve to steady said hand tool for use thereof.